1. Technical Field
The present invention relates to a reaction force generator and more particularly to a reaction force generator configured to generate a reaction force when pressed by an operating member.
2. Description of the Related Art
There is conventionally known a reaction force generator configured to generate a reaction force against an operating member depressed and pivoted by an operator. The reaction force generator includes a protruding dome member made of an elastic material such as rubber. When the reaction force generator is pressed by the operating member, the dome member is deformed, causing the reaction force generator to generate a reaction force against the operating member due to the deformation. Patent Document 1 (Japanese Patent Application Publication No. 2007-25576) discloses such a reaction force generator, for example.
A key operation detection device (i.e., the reaction force generator) disclosed in Patent Document 1 includes a plurality of key switches provided in a resilient protrusion (i.e., the dome member). The key switches are respectively supported by resilient protruding portions specific to the respective key switches. With this construction, when the key operation detection device is pressed by the key as the operating member, the resilient protrusion and the resilient protruding portions specific to the respective key switches are deformed to generate reaction forces. During deformation, a buckling phenomenon occurs on the resilient protrusion, so that a roof of the resilient protrusion is bent inward. The reaction force generated by the deformation of the resilient protrusion greatly changes before and after the buckling phenomenon. Also, a rate of deformation differs between a portion of the resilient protrusion nearer to a pivot fulcrum of the key and a portion of the resilient protrusion farther from the pivot fulcrum, so that the buckling phenomenon occurs at different timings on the portion of the resilient protrusion nearer to the pivot fulcrum and the portion of the resilient protrusion farther from the pivot fulcrum. Accordingly, each time when the buckling phenomenon occurs on the portion of the resilient protrusion nearer to the pivot fulcrum and the portion of the resilient protrusion farther from the pivot fulcrum, the reaction force generated by the key operation detection device greatly changes, inhibiting a smooth change of the reaction force within a range of the pivotal movement of the key (see FIG. 11). As a result, when depressing the key with a finger, the operator may feel uncomfortable with a feel of the depression. For example, the operator may feel a reaction force at a plurality of timings during operation of the key and may feel a reaction force unexpected by the operator.